Biomedical subjects

J Grapperon

Publications and source records attributed to J Grapperon.

7 recordsLinked to original sources

PubMed2000

Is the 'error negativity' specific to errors?

When subjects make an erroneous response in a choice reaction time task, an error negativity, or error-related negativity (N(E)/ERN), peaking at about 100 ms after EMG onset, has been described. This wave is often considered to be absent on correct response trials. We report a small N(E)/ERN wave on correct response trials during a choice reaction time task in which surface Laplacians were estimated by the source derivation method. This wave is well focused at FCz, and its time course is the same for correct responses trials, incorrect sub-threshold EMG activation trials, and error trials. Current source density maps, also indicate a focus at FCz. A second experiment showed the existence of a N(E) at FCz on correct trials during a simple RT task. Rather than an error detection process per se, we propose that the N(E)/ERN reflects either a comparison process leading secondarily to error detection, or an emotional reaction.

Adult↗

PubMed1998

[The contribution of cognitive evoked potentials to knowledge of mechanisms on the Stroop test].

The Stroop test is based on interference between reading and naming of incongruent color words. To decide whether this conflict was of perceptual or motor origin, event-related potentials were simultaneously recorded. Since the components of these potentials are dependent on the progression of information processing, their changes related with the nature of the stimulation should provide information about the mechanisms underlying the conflict. Evoked potentials were recorded from three midline leads in 18 healthy subjects during reading and naming tasks. The 216 stimulations were the words "red, green and blue" presented in either a congruent or incongruent color, or in a neutral color. The behavioral Stroop effect did not affect the P300 latency, suggesting that the conflict occurs in the motor system. This was supported by the presence of a premotor negativity for incongruent stimulations, occurring between 400 and 205 ms before button press, and present in the naming condition only. Moreover, for the two conditions, congruent stimulations evoked positive potentials between 260 and 310 ms at the level of the occipital lead for reading and at the level of the frontal lead for naming. The possibility of an interaction of specialized channels for stimulation analysis at an early level is raised.

Adolescent↗

PubMed1994

[Can neurophysiologic tests differentiate between depression and dementia?].

In order to evaluate the clinical utility of neuro-physiological tests in distinguishing between depression and dementia, we compared quantified EEG and event-related potentials (ERP) in 13 depressed and 12 demented patients. Their cognitive functions were clinically assessed by the ERFC test. When scored with a discriminant function, EEG misclassified one patient and all were well classified with ERP. Nevertheless this exam could be clearly obtained in only 7 demented and 5 depressed patients. Although a therapeutic effect could not be absolutely discarded, these results show that these tests, when practicable, can be helpful when clinical diagnosis is uncertain.

Adult↗

PubMed1993

[Central and peripheral nervous system motor conduction rate in HIV infection].

In order to assess the central motor pathways of HIV-infected patients motor evoked potentials were recorded on the upper limbs after transcranial and cervical magnetic stimulations and compared with peripheral conduction velocities. Motor evoked potentials were measured on both sides of 28 patients, mostly at the AIDS stage. Our results showed that although peripheral neuropathy was often found, central motor pathways did not appear, at the level they were tested, to be directly or indirectly damaged by the virus. On the contrary, some hyperexcitability seemed to be present.

Acquired Immunodeficiency Syndrome↗

PubMed1988

Effects of high pressure on nervous conduction velocity in man.

The velocities of motor and sensory nervous conduction and of neuro-muscular transmission were measured in four subjects during a simulated dive at 4.6 MPa (46 bars). The results show an increase in motor distal latency in the ulnar nerve, especially during decompression, with reversibility of the effect on return to ambient conditions. The hypothesis of an interaction of dissolved gases with the membranes of ischaemic cells is proposed.

Adult↗

PubMed1986

[Changes in nerve conduction velocity as a result of hyperbaria in man].

Nervous conduction was measured in 27 subjects before and after compression in ternary mixture (helium, nitrogen and oxygen) ranging from 5,5 to 12 ATA. Among the eleven parameters studied, three showed an acceleration of the nervous conduction in the distal part of the sensitive and motor fibers. Although no precise mechanism can be established, different factors, in particular the role of ischemia, are discussed.

Adult↗

PubMedDate not supplied

[Stroop test and schizophrenia].

Utilization of the Stroop test with schizophrenic subjects is reviewed from 32 studies published since 1960. This test, in which subject has to name the color of color-words which are congruent or incongruent, is much used as a selective attention test. Its specific disturbance in schizophrenics would confirm the overload of consciousness with unsignificant non filtered information, probably due to lowering of frontal functions. Stroop effect is not always raised in these patients, especially when general slowing is taken into account. Technical differences modify the test power and can explain contradictory results. The thought disorder symptom seems the most correlated with the results of the test, and particular sensitiveness of paranoïd form has been argued. Neuroleptics do not seem to act on Stroop effect. Factors explaining the great variability of patients in this test are not fully put in light. One hypothesis, already raised, is that the test is linked to a particular attentional constitutional aptitude, and whose relations with the illness are to be explained.

Antipsychotic Agents↗